What is the ruling on whoever memorizes the Quran without observing the rules of recitation but he recites without making grammatical errors?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

It is an obligation on a Muslim who wants to recite the Quran or to memorize it, to learn the rules of recitation of the Quran because it is an obligation on him to do so.

Whoever is negligent in learning the rules of the recitation of the Quran while being able to do so, is sinful if he recites it in a way that changes its meaning, but if he makes mistakes that do not change the meaning, then he is not forbidden from reciting it.

Allah Knows best.